Question

900 students attended the school concert. There were twice as many adults as children in the audience. How many children attended the concert? which let statement would you use?

Answer 1

I am slightly confused by your wording in the last sentence, but if you are trying to figure out how many children attended the concert you would use the second statement. The first statement does not tell you if the students are "children" are not so that is not an appropriate choice.